Twisting machines with internal gathering are basically divided into two categories, according to the system used to drive the twisted product winder reel. The reel may be rotated by a constant-speed motor with the interposition of a torque limiter, or by a motor whose speed is variable automatically by means which detect the progressively increasing diameter of the winding on the reel and/or by means which detect variations in longitudinal tension of the twisted product being wound, which for this purpose is run around tensioning means of what is known as the idler type. With twisting machines of the latter type it is possible to avoid undesirable tensions in the twisted products and to keep the electrical conductivity of the wires used unchanged, a condition which is difficult to obtain with twisting machines of the first type.
The production and use of twisting machines of the second type is at present beset by considerable technical difficulties which make it necessary to fall back on twisting machines of the first type the technical difficult are essentially due to the difficulty of producing a reliable electrical connection through slip rings and brushes between the electronic computer disposed in the external control panel of the twisting machine and the various motors and numerous safety and control devices required to control not only the winder reel but also the traversing device and the various mechanisms contributing to the operation of the said type of internal winder. To provide the necessary connection between the internal devices of the twisting machine and the external power supply and control panel, it is at present necessary to provide a slip ring system with a very high number of rings with considerable elongation of the twisting machine. It is then necessary to transmit, through the rings and brushes, electrical signals which may be distorted in an unpredictable way by disturbances arising from the sliding contact between the said brushes and the rings of the slip ring system.